JP4347887B2 - Cell selection techniques for frequency division multiple access systems. - Google Patents

Description

  The present disclosure relates to wireless communication, and more particularly, to a technique for cell selection in a wireless communication system implementing frequency division multiple access (FDMA).

  A wide variety of wireless communication technologies have been developed to facilitate wireless telecommunications. Frequency division multiple access (FDMA) refers to a wireless communication technique in which an allocated frequency spectrum is divided into a plurality of small frequency cells. Each cell of the allocated spectrum has a carrier signal that is modulated with data. Dividing the allocated frequency spectrum into cells increases the amount of data communicated over the spectrum and provides an easy mechanism for allocating bandwidth to service providers. For example, a particular cell can be assigned to a particular service provider, and a given service provider's wireless network can use the assigned cell or cells to provide service to its subscribers. .

  The Global System for Mobile Communication (GSM) standard, standardized by the European Telecommunications Standards Institute (ETSI), is an example of a system that utilizes FDMA technology. In Europe, for example, frequency bands around 900 megahertz (MHz) and 1800 MHz have been allocated for GSM. The frequency bands around 900 and 1800 MHz are divided by GSM into approximately 548 frequency cells of approximately 200 kilohertz (KHz) per cell. These different cells are assigned to different service providers for use in the service provider network. Some cells are used as network beacons to notify subscriber units that have cells associated with a given network, while other cells deliver network traffic to and from mobile subscriber units Used only for. In GSM networks, different frequency cells also utilize time division multiple access (TDMA), where time slots are clearly assigned within the cell, for time-division communication.

  One challenge in systems implementing FDMA technology, such as GSM, is the process of cell selection or acquisition by subscriber units. A subscriber unit refers to a device used by an end user, such as a mobile radiotelephone. In an FDMA system, a subscriber unit scans various cells in the allocated spectrum looking for the most desirable cell for telecommunications. Generally, the most desirable cell is the cell associated with the subscriber unit service provider's network. Alternatively, the cell in which the subscriber unit service provider has a good roaming agreement. For example, when selecting between cells in a given service provider's network, a cell with a higher power signal is also desirable over a lower power cell.

  In one embodiment, the present disclosure measures the power of a first signal associated with a first cell of a frequency division multiple access (FDMA) system and a second associated with a second cell of the FDMA system. The second cell is adjacent to the first cell with respect to frequency, and the measured power of the second signal is measured by the first signal. A method including setting a value indicating the measured power of the second signal to a negligible value when greater than a threshold less than the measured power is described.

  In another embodiment, the present disclosure receives a signal associated with a cell of an FDMA system, the cell spanning a first frequency range, and the signal is transmitted to a second frequency range. A second frequency range is smaller than the first frequency range. The method further includes measuring the power of the filtered signal and identifying an estimate of power associated with the cell.

  In another embodiment, the present disclosure is a receiver that receives a first signal associated with a first cell of an FDMA system and a second signal associated with a second cell of the FDMA system, The second cell measures the power of the receiver adjacent to the first cell with respect to frequency and the first and second signals, and the measured second signal power is measured by the first measured A subscriber unit of an FDMA system is described that includes a control unit that sets a value indicative of the measured second signal power to a negligible value if it is higher than a lower threshold than the signal power.

  In another embodiment, the present disclosure is a receiver that receives a signal associated with a cell of an FDMA system, the cell spanning a first frequency range, and the signal is transmitted to a second frequency. A FDMA system subscriber unit with a control unit that filters to a range, the second frequency range being smaller than the first frequency range is described. In addition, the control unit measures the power of the filtered signal and identifies an estimate of power associated with the cell.

  In another embodiment, the present disclosure causes an FDMA system subscriber unit to measure the power of a first signal associated with a first cell of the FDMA system and is adjacent to the first cell with respect to frequency. Measure the power of the second signal associated with the second cell of the system and measure if the measured second signal power is greater than a threshold that is less than the measured first signal power. A computer-readable medium including instructions for setting a value indicating the power of the second signal to a negligible value will be described.

  In another embodiment, the present disclosure causes a subscriber unit of an FDMA system to receive a signal associated with a cell of an FDMA system that spans a first frequency range, and the signal is transmitted over a first frequency range. A computer readable medium including instructions for filtering to a small second frequency range is described. This instruction also causes the subscriber unit to measure the power of the filtered signal and to identify an estimate of the power associated with the cell.

  In another embodiment, the present disclosure provides means for receiving a first signal associated with a first cell of an FDMA system and a second signal associated with a second cell of the FDMA system, The second cell has a means for measuring the power of the first signal and the second signal with respect to the frequency, a means for measuring the power of the first signal and the second signal, and the power of the measured second signal being measured. A subscriber unit of an FDMA system comprising means for setting a value indicative of the measured second signal power to a negligible value when greater than a threshold less than the first signal power is described. .

  In another embodiment, the present disclosure comprises means for receiving a signal associated with a cell of an FDMA system that spans a first frequency range, and means for filtering the signal to a second frequency range; The second frequency range describes subscriber units of the FDMA system that are smaller than the first frequency range. The subscriber unit also includes means for measuring the power of the filtered signal and identifying an estimate of the power associated with the cell.

  The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and claims.

  The present disclosure is directed to power estimation techniques for use by FDMA system subscriber units during the cell selection process. Power estimation techniques recognize that neighboring cells, ie neighboring cells with respect to frequency, often have a slight overlap. Thus, in practice, even if no signal is present in the neighboring cell, power may be detected in the neighboring cell by the power from the signal associated with one cell. In accordance with this disclosure, techniques are described for identifying, reducing, or eliminating “false positive” detections in such neighboring cells, eg, during a GSM power scan. In this disclosure, the term “false positive” refers to the detection of power in a cell when the signal is not actually in the cell. By identifying, reducing, and eliminating false positive detections, the cell selection process can be accelerated and additional processing of false positive signals in such neighboring cells can be avoided.

  FIG. 1 is a block diagram illustrating a wireless communication system 10 implementing a frequency division multiple access (FDMA) communication technique. For example, system 10 may comprise a Global System for Mobile Communication (GSM) system in accordance with the European Telecommunications Standards Institute (ETSI) GSM standard. The GSM standard uses not only time division multiple access (TDMA) technology in which time-assigned communications are scheduled during specific time slots within a cell, but also FDMA technology in which the frequency band is divided into multiple cells. To do. In the following description, many techniques are described in the context of GSM. However, the same or similar technology can also be used with various other wireless protocols or standards that utilize FDMA.

  The wireless communication system 10 includes a plurality of base stations 12A-12C (collectively base stations 12) that communicate with a subscriber unit 14. Although a single subscriber unit 14 is illustrated, the system 10 generally includes multiple subscriber units. Subscriber unit 14 generally refers to a wireless device used by an end user. For example, in the GSM system, the subscriber unit 14 typically comprises a mobile radiotelephone. However, the subscriber unit 14 is also configured to communicate according to, for example, a desktop or portable computer, personal digital assistant (PDA), interactive television, wireless data terminal, wireless data collection device, or techniques described in this disclosure. It can also be implemented in various other portable computing devices, such as any other wireless device that has been implemented.

  Base station 12 is typically a stationary computer that communicates wirelessly with subscriber unit 14 to provide network access to subscriber unit 14. For example, the base station 12 provides an interface between the subscriber unit 14 and the public switched telephone network (PSTN). This routes telephone calls to and from the subscriber unit 14. Alternatively or additionally, the base station 12 is connected to a packet-based network for transmission of packet-based voice information or packet-based data. Base station 12 is often referred to as a base transceiver system (BTS).

  The wireless communication system 10 operates according to FDMA communication technology. Frequency division multiple access (FDMA) refers to a wireless communication technique in which an allocated frequency spectrum is divided into a plurality of small frequency “cells”. Each cell of the allocated spectrum has a carrier signal that is modulated with data. Each base station 12 typically operates in a different frequency cell of the allocated spectrum.

  One challenge in an FDMA system such as system 10 is the process of cell selection or acquisition by subscriber 14. During the cell selection process, subscriber unit 14 identifies a desired cell that can provide network access to subscriber unit 14. If only one of the base stations 12 is operated by the network provider of the subscriber unit 14, the subscriber unit 14 should identify the cell associated with the base station as the desired communication cell. On the other hand, if two or more of the base stations 12 are operated by the network provider of the subscriber unit 14, the subscriber unit 14 identifies the cell of the network provider with the highest received signal strength. Should. If none of the base stations 12 are operated by the network provider of the subscriber unit 14, the subscriber unit 14 should identify the cell based on other priorities. For example, if none of the base stations 12 is operated by the network provider of the subscriber unit 14, the subscriber unit 14 selects a cell operated by a different network provider in which the preferred roaming agreement is functioning. be able to. Other types of priorities can also be used.

  In FIG. 1, the illustrated elements of subscriber unit 14 are specific elements used in the cell selection process. There are many other elements for other functions such as signal coding and demodulation. However, for simplicity, additional elements are not described.

  The receiver / transmitter 20 receives the radio signals 18A to 18C (collectively the signal 18) from the base station 21 via the antenna 21. The receiver / transmitter 20 also performs various analog signal conditioning functions on the received signal, such as signal filtering or scale. The receiver / transmitter 20 forwards the received signal to an analog-to-digital (A / D) converter 22. The converter 22 samples the analog signal and generates a digital signal. A digital signal sampled from the received analog signal is passed from the A / D converter 22 to the control unit 24. The control unit 24 performs a cell selection process as will be described.

  The control unit 24 includes a number of functional elements implemented, for example, in hardware, software, firmware, etc. to perform the cell selection process. For example, the control unit 24 includes a power scan unit 26, a power estimator 28, an ID generator 30, and a cell selector 32. The control unit 24 can be implemented as a digital signal processor (DSP) that executes software modules. Alternatively, it includes discrete hardware elements. The control unit 24 can be realized by any combination of hardware, software, firmware, one or more programmable microprocessors, a digital signal processor, and the like. The various elements of the control unit 24 are illustrated for illustrative purposes, but can be integrated with other elements, for example, in hardware or software. If implemented in software, a memory or other computer readable medium (not shown) is connected to the control unit 24 for storing software instructions that are loaded into the control unit 24 for execution. The

  The power scan unit 26 scans the cells of the assigned frequency spectrum to separate the different signals associated with the various cells. Again, in GSM, the frequency bands around 900 and 1800 MHz are divided into approximately 548 frequency cells of approximately 200 KHz per cell. In such a case, power scan unit 26 separates the signals associated with each of the 548 cells.

  The power estimator 28 measures and estimates the power of various cells. Further, in accordance with this disclosure, power estimator 28 implements one or more techniques that improve and facilitate the cell selection process. In particular, power estimator 28 accounts for certain factors of system 10. Otherwise, it may distort the accurate power estimation of the cell. The power estimator 28 also maintains a list of cells in the order of the estimated power of the different cells from the highest power cell to the lowest power cell. In accordance with this disclosure, the ordered list of cells is related to the actual power of the various cells measured by the power estimator 28, for example when the power estimator 28 identifies cells that are not likely to be good candidates. It can be corrected.

  The ID generator 30 uses the ordered cells that are held by the power estimator 28. In particular, the ID generator starts with the highest power cell in this list and generates a network ID for that cell. In GSM, the network ID generation process is a multi-step process. For example, for a given cell in GSM, ID generator 30 receives a digital signal from A / D converter 24 and obtains a frequency correction channel (FCCH). This can be used for coarse synchronization to the cell. The ID generator 30 then decodes the synchronization channel (SCH). The SCH provides basic timing information for the appropriate base station 12 associated with each cell. Once the ID generator 30 has an SCH, it decodes an overhead channel, such as a broadcast channel (BCCH), to obtain a public land mobile network (PLMN) code. This identifies the network associated with a given cell.

  The cell selector 32 receives the generated network ID, such as a PLMN code, and selects a desired cell to be used by the subscriber unit 14 in the next telecommunications. The cell selector 32 selects the highest power cell associated with the specific network, but if the cell associated with the specific network is not strong enough, the priority scheme in which other cells are selected. Execute. For example, if none of the base stations 12 is operated by the network provider of the subscriber unit 14, the cell selector 32 may select a cell operated by a different network provider in which the preferred roaming agreement is functioning. Can do. The cell selector 32 then communicates with the base station of the selected cell to register with the respective base station in the selected cell for the next telecommunication with the receiver / transmitter 30. To instruct. There is typically a strong preference for cell usage associated with the network provider that issued the subscriber unit 14. Nevertheless, the selected cell must satisfy the minimum power requirement for reliable communication.

  FIG. 2 is a flowchart for explaining cell selection processing performed by the subscriber unit 14. As shown in FIG. 2, the power scan unit 26 scans the cells of the FDMA frequency spectrum to separate the signals of the different cells into frequency bins (41). Then, the power estimator 28 estimates the power of different cells (42). This causes a channel effect that tends to gradually degrade the reliability of power measurement by the power estimator 28. For example, as outlined in more detail below, the power estimator 28 measures power, but the measured power is a predetermined measured power associated with a cell in an adjacent frequency bin, such as 15 decibels. If it is smaller than the margin, the measured power is adjusted to a value that can be ignored. In this case, the measured power will belong to the power of neighboring cells, but may not belong to the actual cell being measured. Accordingly, such cells are preferably removed from consideration of the cell selection process to avoid false cell detection that would only be to satisfy the desired minimum power requirement due to the overlap effect.

  Alternatively, power estimator 28 may implement a filter technique that can ensure that power associated with neighboring cells does not substantially affect power measurements for a given cell. In particular, filter techniques can be used to narrow the range of frequencies used for power estimation purposes. This reduces the likelihood that signal power from one cell will generate an appearance of signal power for neighboring cells.

  The power estimator 28 sorts the cells based on the estimated power of the cells (43). In particular, the power estimator 28 generates a list of cells in order from the largest to the smallest estimated power. The ID generator 30 generates a network ID for the cell (44). The cell selector 32 selects a desired cell based on the network ID and the estimated power level (45). For example, the ID generator 30 generates a network ID that begins with the highest power cell, and once the cell selector 32 identifies the network ID associated with the service provider of the subscriber unit 14, the power level of that cell is sufficient. If so, the cell is selected, and the ID generation process ends.

  According to the GSM standard, the selected cell is required to be in the 70 strong cells, ie the cell with the highest estimated power level. Thus, if the network ID associated with the service provider of the subscriber unit 14 is not within the 70 strongest cells, the cell selector 32 may, for example, connect the cell to a different service provider with which a preferred roaming agreement has been established. Select cells based on other criteria such as relevant. Once a cell is selected from the 70 highest power estimates (45), the subscriber unit 14 registers with the selected cell (46). For example, the handset / transmitter 30 transmits this registration information to one of the base stations 12 associated with the selected cell and then sends this cell for a call to the subscriber unit 14. use.

  In telecommunications protocols that use GSM and other FDMA, neighboring cells often have a slight frequency overlap. Thus, if a signal is present in one cell, the signal will be the power measurement of an adjacent cell, i.e. a cell having a frequency band immediately adjacent to the frequency band of the cell where the signal actually exists. May have an impact. In particular, a signal in a given cell has a frequency component that is substantially concentrated in the associated frequency band, but extends to neighboring cells. This overlap effect lengthens the cell selection process due to erroneous detection of neighboring cells.

  When a signal is present in the first GSM cell, a cell that is immediately adjacent to this first cell generally has this first cell even if no signal is actually present in this neighboring cell. It shows a signal about 16 decibels lower than the cell. Furthermore, in some cases, a signal that is about 16 decibels lower than this first cell causes neighboring cells to be present in the 70 strong cells so that they can be further processed according to the GSM standard. Be a candidate for. If nothing is evident for this overlap effect, the subscriber unit 14 may actually do so to ensure that 70 strong power cells are actually being considered by the cell selector 32. (3 × 69 + 1) = 207 cells need to be processed. This adds significant time and processing overhead to the cell selection process.

  A more preferred approach is to attempt to remove the neighboring cell from consideration if the power in the neighboring cell is only brought about by the presence of a signal in the first cell. Subscriber unit 14 can improve the cell selection process by revealing this overlap effect. Two alternative embodiments to account for this overlap effect are described in detail below.

  The first approach identifies a “false positive” if the measured cell power is a predetermined value less than the neighbor cell power, for example, 15 decibels lower than that of the neighbor cell. In that case, this cell is declared false positive and the power estimated for that cell can be set to a negligible value. The second approach implements a filter technique for power estimation. In particular, upon receiving a signal associated with a cell that spans a first frequency range, the signal can be filtered to a second frequency range. Here, the second frequency range is smaller than the first frequency range. The measured power of this filtered signal is then used to identify an estimate of power associated with the cell. Such special filtering for power estimation can substantially reduce power overlap between neighboring cells.

  FIG. 3 is a block diagram of a subscriber unit 14A corresponding to the subscriber unit 14 of FIG. In this case, the subscriber unit 14 </ b> A includes a power estimator 28 </ b> A including an estimator 51, a comparison unit 52, and a priority unit 53. The comparison unit 52 makes a “false positive” if the power of the cell measured by the estimator 51 is a predetermined value less than the power of the neighboring cell, eg, 15 decibels lower than that of the neighboring cell. Identify. In this case, the comparison unit 52 can declare a false positive and set the estimated power for that cell to a negligible value. This allows it to be excluded from consideration from among the highest power cells scanned by the subscriber unit 14. In particular, based on an estimated power value that can be ignored, priority unit 53 prioritizes the cell with a very low priority.

  The handset / transmitter 20 receives a wireless signal via the antenna 21 and performs various analog signal conditioning functions, such as a filter or a scale, on the received signal. The receiver / transmitter 20 transfers the received signal to an analog-to-digital (A / D) converter 22. This samples this signal to produce a digital signal. A digital signal indicating the received analog signal is passed from the A / D converter 22 to the control unit 24A. The control unit 24A performs a cell selection process.

The power scan unit 26 scans the cells of the assigned frequency spectrum to separate the different signals associated with the various cells. The power estimator 28A performs techniques that can measure and estimate the power of various cells and accelerate the cell selection process. In particular, the estimator 51 measures the power of a given cell, and the comparison unit 52 compares the measured power of that cell with the measured power associated with the cell adjacent to that cell with respect to frequency. If the comparison unit 52 determines that the measured power is a predetermined value lower than the power of the neighboring cell, eg, 15 decibels lower than the power of the neighboring cell, the comparison unit 52 is estimated for that cell. Set the power value to a value that can be ignored. The priority unit 53 will then prioritize this cell with a very low priority based on the value set by the comparison unit. On the other hand, if the comparison unit 52, the measured power and than a predetermined value than the power in the neighbor cell is determined that low wards, power priority unit 53 is measured by estimator 51 for that cell Prioritize the cell based on

  The ID generator 30 uses an ordered list maintained by the priority unit 53. In particular, the ID generator starts with the highest power cell in the list and generates a network ID for that cell. And also in the context of GSM, the ID generator 30 obtains the frequency correction channel (FCCH), decodes the synchronization channel (SCH), and finally decodes the broadcast control channel (BCCH) to move public land Obtain a network (PLMN) code. This identifies the network associated with a given cell.

  The cell selector 32 receives the generated network ID, such as a PLMN code, and selects a desired cell to be used by the subscriber unit 14 in the next telecommunications. In accordance with this disclosure, network ID acquisition should not be attempted for a false positive cell where the cell power may belong to the neighbor cell power. This is because power estimator 28A identifies and reduces power for such false positive cells. In this way, the cell selection process can be improved. This avoids any processing delays associated with resolving network IDs for false positive cells in another way.

FIG. 4 is a flowchart showing processing performed by the power estimator 28A of FIG. As shown in FIG. 4, the estimator 51 measures the power of the first cell (61), and then measures the power of the second cell. This is adjacent to the first cell (62). The comparison unit 52 maintains a table that lists the measured power of various cells. Compare unit 52 determines the power of the second cell, the lower squid than the value obtained by subtracting a predetermined margin X from the power of the first cell. Here, X represents a defined value such as between 10 and 20 decibels depending on, for example, filtering (63). For example, this value X can be about 15 decibels. In any case, if the comparison unit 52 determines that the power of the second cell is lower than the power of the first cell minus the margin X (yes in 63), the comparison unit 52 A value indicating the estimated power of the second cell is set to a negligible value (64). The priority unit 53 will prioritize this cell with a very low priority based on the value set by the comparison unit. On the other hand, if the comparison unit 52 determines that the power of the second cell is higher than the value of the power of the first cell minus the margin X (no in 63), no adjustment is made. In that case, priority unit 53 prioritizes this cell based on the power measured by estimator 51 for that cell.

  In accordance with this disclosure, the process of FIG. 4 may be applied with respect to two cells immediately adjacent to a given cell. In other words, for each cell, the process of FIG. 4 is performed on, for example, the first cell with a slightly lower center frequency than the current cell and the later cell with a slightly higher center frequency than the current cell. Can be applied. In other words, the “second cell” referred to in FIG. 4 corresponds to either the first cell or the later cell, and this process applies to both those cells adjacent to the first cell. Can be done. Furthermore, the process of FIG. 4 is repeated for each of a plurality of cells in the allocated spectrum.

  FIG. 5 is a block diagram of a subscriber unit 14B corresponding to the subscriber unit 14 of FIG. In this case, according to another embodiment, the subscriber unit 14B comprises a power estimator 28B. The power estimator 28 </ b> B includes a filter 71, an estimator 72, and a priority unit 73. Filter 71 receives a signal associated with a cell that spans X frequency ranges and filters this signal to Y frequency ranges. Here, Y is smaller than X. The estimator 72 measures the power of the filtered signal to identify an estimate of power associated with this cell. By filtering this cell to a smaller frequency range than this cell, the effect of power overlap of neighboring cells can be substantially reduced or eliminated. Thus, the power estimate maintained by priority unit 73 should not include any false positives where the measured power is distorted by the presence of signals in neighboring cells.

  Like in the subscriber unit 14A (FIG. 3), in the subscriber unit 14B (FIG. 5), the receiver / transmitter 20 receives a radio signal via the antenna 21. Implement various analog signal processing functions such as filters and scales. The receiver / transmitter 20 transfers the received signal to an analog-to-digital (A / D) converter 22. The converter 22 samples this signal to generate a digital signal. A digital signal indicating the received analog signal is passed from the A / D converter 22 to the control unit 24B. The control unit 24B performs a cell selection process.

  The power scan unit 26 scans the cells of the assigned frequency spectrum to separate the different signals associated with the various cells. The power estimator 28B performs techniques that can measure and estimate the power of various cells and accelerate the cell selection process. Filter 71 receives a signal associated with a cell that spans X frequency ranges and filters this signal to Y frequency ranges. Here, Y is smaller than X. In particular, the frequency range Y falls within the frequency range X and is narrower than the frequency range X. Thus, the narrower frequency range Y tends to remove the effect of neighboring cells. For example, in GSM, the value of X corresponds to about 200 KHz. Because it is approximately the width of the cell. In that case, the value Y may be about 100 KHz centered around the approximate center frequency of a given cell.

  An estimator 72 then measures the power of the filtered signal to identify an estimate of power associated with that cell. By filtering the cell to a smaller frequency range than this cell, the power overlap of neighboring cells can be substantially reduced or eliminated. Accordingly, the power estimate maintained by priority unit 73 should not include any false positives where the measured power is distorted by the presence of signals in neighboring cells.

  FIG. 6 is a flowchart showing processing performed by the power estimator 28B of FIG. As shown in FIG. 6, filter 71 receives a cell signal at a frequency width associated with the cell (81) and filters the signal to a frequency width less than the frequency width associated with the cell (82). . For example, a 200 KHz cell ranging from 900,000 KHz to 900,200 KHz can be filtered to a 100 KHz width ranging from 900,050 KHz to 900,150 KHz, even though the desired filter range is imposed on various implementations. . In any case, the estimator 72 generates a cell power estimate based on the filtered signal strength (83). Since the signal associated with the cell is filtered to a frequency range that is smaller than that of this cell, the power overlap of neighboring cells can be substantially reduced or eliminated.

  The process of FIG. 6 is repeated for each of a plurality of cells in the allocated spectrum.

  A number of implementations have been described. In particular, power estimation techniques have been described. This accounts for signal overlap between adjacent cells in an FDMA system. This technique is implemented in the subscriber unit 14 in hardware, software, firmware, etc. to perform cell selection or manual PLMN list generation. Cell selection generally refers to a search for a specifically desired PLMN. Once the desired PLMN is identified, the PLMN acquisition can be stopped. Manual PLMN list generation generally refers to the process of manually instructing the subscriber unit to display all available networks so that the user can select a network. In manual PLMN list generation, the subscriber unit obtains network IDs for many high power cells in this list. In accordance with this disclosure, either cell selection or manual PLMN list generation is accelerated using one or more of the techniques described herein.

  An example hardware implementation is a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a programmable logic device, a specially designed hardware element, or any combination thereof Including implementation within. Further, one or more of the techniques described herein may be implemented partially or wholly in software. In that case, the computer readable medium may store or include computer readable instructions, ie, program code executed by the DSP or processor of the subscriber unit to perform one or more of the techniques described above.

  For example, the computer readable medium may be random access memory (RAM), read only memory (ROM), non-volatile random access memory (NVRAM), electronically erasable programmable connected to the control unit 24 of the subscriber unit 14. It may include read only memory (EEPROM), flash memory, and the like. In that case, the control unit 24 includes a DSP or processor that executes various software modules stored on a computer-readable medium. Many other modifications may be made without departing from the spirit and scope of the present disclosure. Accordingly, these and other embodiments are within the scope of the claims.

FIG. 1 is a block diagram illustrating a wireless communication system implementing FDMA communication techniques in accordance with the teachings of this disclosure. FIG. 2 is a flow diagram illustrating cell selection processing performed by a subscriber unit of a wireless communication system. FIG. 3 is a block diagram of one embodiment of a subscriber unit in accordance with the present disclosure. FIG. 4 is a flowchart showing the processing performed in the subscriber unit described in FIG. FIG. 5 is a block diagram of another embodiment of a subscriber unit according to the present disclosure. FIG. 6 is a flow diagram illustrating processing performed within the subscriber unit shown in FIG.

Claims (19)

Measuring the power of a first signal associated with a first cell of a frequency division multiple access (FDMA) system;
The method comprising: measuring power of a second signal associated with a second cell of said frequency division multiple access (FDMA) system, a frequency band of the second cell, the frequency band of the first cell Being adjacent,
A value indicating the measured power of the second signal when the measured power of the second signal is lower than a value obtained by subtracting a predetermined value from the measured power of the first signal; And setting to a negligible value.   The method of claim 1, wherein the frequency division multiple access (FDMA) system comprises a global system for mobile communications (GSM) system.   The method of claim 1, wherein the negligible value is approximately equal to zero.   The method of claim 1, wherein the threshold is approximately in the range of 10 to 20 decibels.   The method of claim 4, wherein the threshold is about 15 decibels. The method of claim 1, wherein
Measuring the power of a plurality of signals associated with a plurality of cells of the frequency division multiple access (FDMA) system;
A value indicative of the power measured for a given one of the plurality of signals associated with a given cell is one of the plurality of signals associated with a cell adjacent to the given cell. from the measured power is lower than the value obtained by subtracting a predetermined value for further method comprising and setting a value indicating the power, to negligible values. The method of claim 6, wherein
Prioritizing the plurality of signals based on a value indicative of the measured power of the signals;
Selecting a desired one of the cells based at least in part on the prioritization;
Registering with a network associated with the desired cell. A subscriber unit of a frequency division multiple access (FDMA) system, comprising:
A receiver for receiving a first signal associated with a first cell of the frequency division multiple access (FDMA) system and a second signal associated with a second cell of the frequency division multiple access (FDMA) system. The frequency band of the second cell is adjacent to the frequency band of the first cell;
When the power of the first and second signals is measured, and the power of the measured second signal is lower than a value obtained by subtracting a predetermined value from the power of the measured first signal And a control unit for setting a value indicating the measured power of the second signal to a negligible value. The subscriber unit of claim 8 , wherein the frequency division multiple access (FDMA) system comprises a global system for mobile communications (GSM) system. 9. A subscriber unit according to claim 8 , wherein the negligible value is approximately equal to zero. 9. A subscriber unit according to claim 8 , wherein the threshold is approximately in the range of 10 to 20 decibels. 9. A subscriber unit according to claim 8 , wherein the threshold is about 15 decibels. The subscriber unit according to claim 8 ,
The receiver receives a plurality of signals associated with a plurality of cells of the frequency division multiple access (FDMA) system;
The control unit has a plurality of signals associated with a cell adjacent to the given cell with a value indicative of power measured for a given one of the plurality of signals associated with the given cell. A subscriber unit that sets a value indicative of said power to a negligible value when it is lower than a value obtained by subtracting a predetermined value from the power measured for one of the two . 14. A subscriber unit according to claim 13 ,
The control unit prioritizes the plurality of signals based on a value indicating the power of the measured signal and selects a desired one of the cells based at least in part on the prioritization. A subscriber unit that causes the subscriber unit to register with a network associated with the desired cell. Having a subscriber unit of a frequency division multiple access (FDMA) system measure the power of a first signal associated with a first cell of the frequency division multiple access (FDMA);
Frequency band, to measure the power of a second signal associated with a second cell of said first of said frequency division multiple access is adjacent to the frequency band of the cell (FDMA),
If the measured power of the second signal is lower than a value obtained by subtracting a predetermined value from the power of the measured first signal, a value indicating the power of the measured second signal, A computer readable medium containing instructions that cause it to be set to a negligible value. The computer-readable medium of claim 15 , wherein the frequency division multiple access (FDMA) system comprises a Global System for Mobile Communication (GSM) system. The computer readable medium of claim 15 , wherein the threshold is approximately in the range of 10 to 20 decibels. A subscriber unit of a frequency division multiple access (FDMA) system, comprising:
Means for receiving a first signal associated with a first cell of a frequency division multiple access (FDMA) system and a second signal associated with a second cell of the frequency division multiple access (FDMA) system; The frequency band of the second cell is adjacent to the frequency band of the first cell;
Means for measuring the power of the first signal and the second signal;
If the measured power of the second signal is lower than a value obtained by subtracting a predetermined value from the power of the measured first signal, a value indicating the power of the measured second signal, A subscriber unit with means for setting to a negligible value. The subscriber unit of claim 18 , wherein the frequency division multiple access (FDMA) system comprises a global system for mobile communications (GSM) system, and the threshold is approximately in the range of 10 to 20 decibels. .

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